Conventionally, image forming apparatuses adopting an electrophotographic system and so on have been put into practical use. It is known that when performing printing in a state where the humidity inside the apparatus is high, the image forming apparatus might cause a failure of print image quality.
Specifically, the image forming apparatus adopting an electrophotographic system, and so on may sometimes perform printing in a state where a ratio (hereinafter, called a moisture absorption ratio) in which a printing sheet (hereinafter, simply called a sheet), that is an image recording medium, absorbs moisture is high. When performing printing in the state where the moisture absorption ratio is high, the image forming apparatus, at the time of transferring a toner image carried on an image carrier of the image forming apparatus to a sheet, generates a transfer failure and so on of the toner image to the sheet, and thereby might cause a failure of print image quality.
In contrast, the conventional image forming apparatus has a heater (a damp heater) for preventing dew condensation, so that receiving the influence of the air temperature and humidity around the image forming apparatus, a sheet does not generate dew condensation or absorb moisture. The damp heater is a heater of about 5-10 W which is arranged for each sheet feeding cassette for housing a sheet, for example. Even when the main power source is in an OFF state, the image forming apparatus energizes the damp heater at any time.
However, in order to perform the above-described moisture absorption measure to a sheet, the image forming apparatus continues to consume electric power for the damp heater, even when the main power source is OFF.